IF you are moving a working Operating system drive from one Dell to another it will USUALLY work,
though you will likely have to download and install the appropriate drivers to get it to do so....
Some computers, for an example HP/Compaq will let you do so proveded that the computers in
question are similar.
Often on identical models from the same mfg it won't ask for the product code.
IF it doesn't ask? don't worry about it.
On my Fujitsu ST-Series tablet computer even moving the OS to a new physical HDD
(say like when you are upgrading your HDD? and then installing that "Cloned copy" back
into the computer the OS came from it will ask you to "Reactivate" windows.
(entering the product code on the CoA)
"Recent hardware changes make it necissary for you to reactive windows"
You enter the product code...If this works you have nothing to worry about.
If it doesn't there are other things you can do...